From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933018AbdJaX2Y (ORCPT ); Tue, 31 Oct 2017 19:28:24 -0400 Received: from mga03.intel.com ([134.134.136.65]:52245 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932971AbdJaX2W (ORCPT ); Tue, 31 Oct 2017 19:28:22 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.44,326,1505804400"; d="scan'208";a="330306474" Subject: [PATCH 04/15] brd: remove dax support From: Dan Williams To: linux-nvdimm@lists.01.org Cc: Jens Axboe , akpm@linux-foundation.org, Matthew Wilcox , linux-kernel@vger.kernel.org, linux-xfs@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, Ross Zwisler , hch@lst.de Date: Tue, 31 Oct 2017 16:21:57 -0700 Message-ID: <150949211688.24061.1197869674847507598.stgit@dwillia2-desk3.amr.corp.intel.com> In-Reply-To: <150949209290.24061.6283157778959640151.stgit@dwillia2-desk3.amr.corp.intel.com> References: <150949209290.24061.6283157778959640151.stgit@dwillia2-desk3.amr.corp.intel.com> User-Agent: StGit/0.17.1-9-g687f MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org DAX support in brd is awkward because its backing page frames are distinct from the ones provided by pmem, dcssblk, or axonram. We need pfn_t_devmap() entries to fully support DAX, and the limited DAX support for pfn_t_special() page frames is not interesting for brd when pmem is already a superset of brd. Lastly, brd is the only dax capable driver that may sleep in its ->direct_access() implementation. So it causes a global burden with no net gain of kernel functionality. For all these reasons, remove DAX support. Cc: Jens Axboe Cc: Matthew Wilcox Cc: Ross Zwisler Signed-off-by: Dan Williams --- drivers/block/Kconfig | 12 --------- drivers/block/brd.c | 65 ------------------------------------------------- 2 files changed, 77 deletions(-) diff --git a/drivers/block/Kconfig b/drivers/block/Kconfig index 2dfe99b328f8..da8bf0268ade 100644 --- a/drivers/block/Kconfig +++ b/drivers/block/Kconfig @@ -297,7 +297,6 @@ config BLK_DEV_SX8 config BLK_DEV_RAM tristate "RAM block device support" - select DAX if BLK_DEV_RAM_DAX ---help--- Saying Y here will allow you to use a portion of your RAM memory as a block device, so that you can make file systems on it, read and @@ -333,17 +332,6 @@ config BLK_DEV_RAM_SIZE The default value is 4096 kilobytes. Only change this if you know what you are doing. -config BLK_DEV_RAM_DAX - bool "Support Direct Access (DAX) to RAM block devices" - depends on BLK_DEV_RAM && FS_DAX - default n - help - Support filesystems using DAX to access RAM block devices. This - avoids double-buffering data in the page cache before copying it - to the block device. Answering Y will slightly enlarge the kernel, - and will prevent RAM block device backing store memory from being - allocated from highmem (only a problem for highmem systems). - config CDROM_PKTCDVD tristate "Packet writing on CD/DVD media (DEPRECATED)" depends on !UML diff --git a/drivers/block/brd.c b/drivers/block/brd.c index 2d7178f7754e..b2391bbd7e5a 100644 --- a/drivers/block/brd.c +++ b/drivers/block/brd.c @@ -20,11 +20,6 @@ #include #include #include -#ifdef CONFIG_BLK_DEV_RAM_DAX -#include -#include -#include -#endif #include @@ -44,9 +39,6 @@ struct brd_device { struct request_queue *brd_queue; struct gendisk *brd_disk; -#ifdef CONFIG_BLK_DEV_RAM_DAX - struct dax_device *dax_dev; -#endif struct list_head brd_list; /* @@ -112,9 +104,6 @@ static struct page *brd_insert_page(struct brd_device *brd, sector_t sector) * restriction might be able to be lifted. */ gfp_flags = GFP_NOIO | __GFP_ZERO; -#ifndef CONFIG_BLK_DEV_RAM_DAX - gfp_flags |= __GFP_HIGHMEM; -#endif page = alloc_page(gfp_flags); if (!page) return NULL; @@ -334,43 +323,6 @@ static int brd_rw_page(struct block_device *bdev, sector_t sector, return err; } -#ifdef CONFIG_BLK_DEV_RAM_DAX -static long __brd_direct_access(struct brd_device *brd, pgoff_t pgoff, - long nr_pages, void **kaddr, pfn_t *pfn) -{ - struct page *page; - - if (!brd) - return -ENODEV; - page = brd_insert_page(brd, (sector_t)pgoff << PAGE_SECTORS_SHIFT); - if (!page) - return -ENOSPC; - *kaddr = page_address(page); - *pfn = page_to_pfn_t(page); - - return 1; -} - -static long brd_dax_direct_access(struct dax_device *dax_dev, - pgoff_t pgoff, long nr_pages, void **kaddr, pfn_t *pfn) -{ - struct brd_device *brd = dax_get_private(dax_dev); - - return __brd_direct_access(brd, pgoff, nr_pages, kaddr, pfn); -} - -static size_t brd_dax_copy_from_iter(struct dax_device *dax_dev, pgoff_t pgoff, - void *addr, size_t bytes, struct iov_iter *i) -{ - return copy_from_iter(addr, bytes, i); -} - -static const struct dax_operations brd_dax_ops = { - .direct_access = brd_dax_direct_access, - .copy_from_iter = brd_dax_copy_from_iter, -}; -#endif - static const struct block_device_operations brd_fops = { .owner = THIS_MODULE, .rw_page = brd_rw_page, @@ -450,21 +402,8 @@ static struct brd_device *brd_alloc(int i) sprintf(disk->disk_name, "ram%d", i); set_capacity(disk, rd_size * 2); -#ifdef CONFIG_BLK_DEV_RAM_DAX - queue_flag_set_unlocked(QUEUE_FLAG_DAX, brd->brd_queue); - brd->dax_dev = alloc_dax(brd, disk->disk_name, &brd_dax_ops); - if (!brd->dax_dev) - goto out_free_inode; -#endif - - return brd; -#ifdef CONFIG_BLK_DEV_RAM_DAX -out_free_inode: - kill_dax(brd->dax_dev); - put_dax(brd->dax_dev); -#endif out_free_queue: blk_cleanup_queue(brd->brd_queue); out_free_dev: @@ -504,10 +443,6 @@ static struct brd_device *brd_init_one(int i, bool *new) static void brd_del_one(struct brd_device *brd) { list_del(&brd->brd_list); -#ifdef CONFIG_BLK_DEV_RAM_DAX - kill_dax(brd->dax_dev); - put_dax(brd->dax_dev); -#endif del_gendisk(brd->brd_disk); brd_free(brd); }